光蒸发风中的沙尘夹带
On dust entrainment in photoevaporative winds
摘要：
利用尘埃光滑粒子流体动力学（SPH）研究了原行星盘中光蒸发风对尘埃的卷吸作用。我们使用不等质量的颗粒来解决超过五个数量级的光盘/流出密度和一个流体配方，有效地模拟阻力停止时间的等效幅度范围。我们发现，只有微米大小的尘埃颗粒和更小的可以夹带在EUV驱动的风。最大粒度由沉降在圆盘中的灰尘而不是风中的空气动力学阻力设定。更一般地说，基流密度与风中最大可分散粒度之间存在线性关系。当尘埃颗粒与低密度风分离时，在圆盘的临界半径处的高层大气中可能发生微米级尘埃颗粒的堆积。卷吸是圆盘中位置的一个强功能，导致流出物中颗粒的大小分选-最大的颗粒在$10$- $20\,$ AU之间进行。每种粒度的粉尘密度峰值出现在其自身夹带区域的内边缘。
英文摘要：
We investigate dust entrainment by photoevaporative winds in protoplanetary discs using dusty smoothed particle hydrodrodynamics (SPH). We use unequal-mass particles to resolve more than five orders of magnitude in disc/outflow density and a one-fluid formulation to efficiently simulate an equivalent magnitude range in drag stopping time. We find that only micron sized dust grains and smaller can be entrained in EUV driven winds. The maximum grain size is set by dust settling in the disc rather than aerodynamic drag in the wind. More generally, there is a linear relationship between the base flow density and the maximum entrainable grain size in the wind. A pileup of micron sized dust grains can occur in the upper atmosphere at critical radii in the disc as grains decouple from the low-density wind. Entrainment is a strong function of location in the disc, resulting in a size sorting of grains in the outflow---the largest grain being carried out between $10$--$20\,$AU. The peak dust density for each grain size occurs at the inner edge of its own entrainment region.
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